Method and apparatus for transmitting signals by prioritizing RLC entities in wireless communication system

ABSTRACT

The present invention relates to a method for transmitting signals by a transmission end in a wireless communication system. In particular, the method includes the steps of: configuring one Packet Data Convergence Protocol (PDCP) entity, at least one first RLC entity related to the one PDCP entity and at least one second RLC entity related to the one PDCP entity; determining whether a service data unit (SDU) to be transmitted is a special SDU or not; if the SDU is the special SDU, transmitting the SDU to the at least one first RLC entity; and if the SDU is not the special SDU, transmitting the SDU to the at least one second RLC entity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/975,915, filed on Aug. 26, 2020, which is a National Stageapplication under 35 U.S.C. § 371 of International Application No.PCT/KR2019/004497, filed on Apr. 15, 2019, which claims the benefit ofKorean Application No. 10-2018-0052008, filed on May 4, 2018. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system.Especially, the present invention relates to transmitting signals byprioritizing Radio Link Control (RLC) entities of a transmission end ina wireless communication system.

BACKGROUND

Introduction of new radio communication technologies has led toincreases in the number of user equipments (UEs) to which a base station(BS) provides services in a prescribed resource region, and has also ledto increases in the amount of data and control information that the BStransmits to the UEs. Due to typically limited resources available tothe BS for communication with the UE(s), new techniques are needed bywhich the BS utilizes the limited radio resources to efficientlyreceive/transmit uplink/downlink data and/or uplink/downlink controlinformation. In particular, overcoming delay or latency has become animportant challenge in applications whose performance critically dependson delay/latency.

SUMMARY

Accordingly, an object of the present invention is to provide a methodof transmitting signals by prioritizing Radio Link Control (RLC)entities of a transmission end in a wireless communication system andapparatus therefore.

The object of the present invention can be achieved by a method fortransmitting signals by a transmission end in a wireless communicationsystem comprises the steps of: configuring one Packet Data ConvergenceProtocol (PDCP) entity, at least one first RLC entity related to the onePDCP entity and at least one second RLC entity related to the one PDCPentity; determining whether a service data unit (SDU) to be transmittedis a special SDU or not; if the SDU is the special SDU, transmitting theSDU to the at least one first RLC entity; and if the SDU is not thespecial SDU, transmitting the SDU to the at least one second RLC entity.

Further, a transmission end in a wireless communication according to theembodiment of the present invention comprises a memory, and at least oneprocessor coupled to the memory. Especially, the at least one processoris configured to configure one PDCP entity, at least one first RLCentity related to the one PDCP entity and at least one second RLC entityrelated to the one PDCP entity, determine whether a SDU to betransmitted is a special SDU or not, if the SDU is the special SDU,transmit the SDU to the at least one first RLC entity, and if the SDU isnot the special SDU, transmit the SDU to the at least one second RLCentity.

Preferably, a priority of the at least one first RLC entity is higherthan a priority of the at least one second RLC entity.

Preferably, the special SDU comprises at least one of a Service DataAdaptation Protocol (SDAP) control SDU, a Transmission Control Protocol(TCP) ACK packet and a Robust Header Compression (ROHC) context updatepacket.

More preferably, if the number of the at least one first RLC entity isgreater than 1 and if the SDU is the special SDU, the special SDU isduplicated as much as the number of the at least one first RLC entity,and the duplicated special SDUs are transmitted to the at least onefirst RLC entity.

More preferably, if the SDU is the special SDU, a PDCP entity of thereception end delivers the special SDU to an upper layer withoutperforming re-ordering procedure.

According to the aforementioned embodiments of the present invention,RLC entities can be prioritized efficiently.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network structure of anevolved universal mobile telecommunication system (E-UMTS) as anexemplary radio communication system;

FIG. 2 is a block diagram illustrating an example of an evolveduniversal terrestrial radio access network (E-UTRAN);

FIG. 3 is a block diagram depicting an example of an architecture of atypical E-UTRAN and a typical EPC;

FIG. 4 is a diagram showing an example of a control plane and a userplane of a radio interface protocol between a UE and an E-UTRAN based ona 3GPP radio access network standard;

FIG. 5 is a diagram showing an example of a physical channel structureused in an E-UMTS system;

FIGS. 6A and 6B illustrate an example of protocol stacks of a nextgeneration wireless communication system;

FIG. 7 illustrates an example of a data flow example at a transmittingdevice in the NR system;

FIG. 8 illustrates an example of a slot structure available in a newradio access technology (NR);

FIG. 9 shows an example about transmitting side operation using RLCentity prioritization according to an embodiment of the presentinvention.

FIG. 10 shows a flow chart for transmitting signals by transmitting sideaccording to an embodiment of the present invention.

FIG. 11 is a block diagram illustrating an example of elements of atransmitting device 100 and a receiving device 200 according to someimplementations of the present disclosure.

DETAILED DESCRIPTION

The technical objects that can be achieved through the presentdisclosure are not limited to what has been particularly describedhereinabove and other technical objects not described herein will bemore clearly understood by persons skilled in the art from the followingdetailed description.

FIG. 1 is a diagram illustrating an example of a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aUniversal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1 , the E-UMTS includes a User Equipment (UE), eNodeBs (eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

As more and more communication devices demand larger communicationcapacity, there is a need for improved mobile broadband communicationcompared to existing RAT. Also, massive machine type communication(MTC), which provides various services by connecting many devices andobjects, is one of the major issues to be considered in the nextgeneration communication. In addition, a communication system designconsidering a service/UE sensitive to reliability and latency is beingdiscussed. The introduction of next-generation RAT, which takes intoaccount such advanced mobile broadband communication, massive MTC(mMCT), and ultra-reliable and low latency communication (URLLC), isbeing discussed.

Reference will now be made in detail to the exemplary implementations ofthe present disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description, which will be givenbelow with reference to the accompanying drawings, is intended toexplain exemplary implementations of the present disclosure, rather thanto show the only implementations that can be implemented according tothe disclosure. The following detailed description includes specificdetails in order to provide a thorough understanding of the presentdisclosure. However, it will be apparent to those skilled in the artthat the present disclosure may be practiced without such specificdetails.

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE. For convenience of description, implementations ofthe present disclosure are described in regards to a 3GPP based wirelesscommunication system. However, the technical features of the presentdisclosure are not limited thereto. For example, although the followingdetailed description is given based on a mobile communication systemcorresponding to a 3GPP based system, aspects of the present disclosurethat are not limited to 3GPP based system are applicable to other mobilecommunication systems.

For example, the present disclosure is applicable to contention basedcommunication such as Wi-Fi as well as non-contention basedcommunication as in the 3GPP based system in which a BS allocates aDL/UL time/frequency resource to a UE and the UE receives a DL signaland transmits a UL signal according to resource allocation of the BS. Ina non-contention based communication scheme, an access point (AP) or acontrol node for controlling the AP allocates a resource forcommunication between the UE and the AP, whereas, in a contention basedcommunication scheme, a communication resource is occupied throughcontention between UEs which desire to access the AP. The contentionbased communication scheme will now be described in brief. One type ofthe contention based communication scheme is carrier sense multipleaccess (CSMA). CSMA refers to a probabilistic media access control (MAC)protocol for confirming, before a node or a communication devicetransmits traffic on a shared transmission medium (also called a sharedchannel) such as a frequency band, that there is no other traffic on thesame shared transmission medium. In CSMA, a transmitting devicedetermines whether another transmission is being performed beforeattempting to transmit traffic to a receiving device. In other words,the transmitting device attempts to detect presence of a carrier fromanother transmitting device before attempting to perform transmission.Upon sensing the carrier, the transmitting device waits for anothertransmission device which is performing transmission to finishtransmission, before performing transmission thereof. Consequently, CSMAcan be a communication scheme based on the principle of “sense beforetransmit” or “listen before talk”. A scheme for avoiding collisionbetween transmitting devices in the contention based communicationsystem using CSMA includes carrier sense multiple access with collisiondetection (CSMA/CD) and/or carrier sense multiple access with collisionavoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wiredlocal area network (LAN) environment. In CSMA/CD, a personal computer(PC) or a server which desires to perform communication in an Ethernetenvironment first confirms whether communication occurs on a networkand, if another device carries data on the network, the PC or the serverwaits and then transmits data. That is, when two or more users (e.g.PCs, UEs, etc.) simultaneously transmit data, collision occurs betweensimultaneous transmission and CSMA/CD is a scheme for flexiblytransmitting data by monitoring collision. A transmitting device usingCSMA/CD adjusts data transmission thereof by sensing data transmissionperformed by another device using a specific rule. CSMA/CA is a MACprotocol specified in IEEE 802.11 standards. A wireless LAN (WLAN)system conforming to IEEE 802.11 standards does not use CSMA/CD whichhas been used in IEEE 802.3 standards and uses CA, i.e. a collisionavoidance scheme. Transmission devices always sense carrier of a networkand, if the network is empty, the transmission devices wait fordetermined time according to locations thereof registered in a list andthen transmit data. Various methods are used to determine priority ofthe transmission devices in the list and to reconfigure priority. In asystem according to some versions of IEEE 802.11 standards, collisionmay occur and, in this case, a collision sensing procedure is performed.A transmission device using CSMA/CA avoids collision between datatransmission thereof and data transmission of another transmissiondevice using a specific rule.

In the present disclosure, a user equipment (UE) may be a fixed ormobile device. Examples of the UE include various devices that transmitand receive user data and/or various kinds of control information to andfrom a base station (BS). The UE may be referred to as a terminalequipment (TE), a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, etc. Inaddition, in the present disclosure, a BS generally refers to a fixedstation that performs communication with a UE and/or another BS, andexchanges various kinds of data and control information with the UE andanother BS. The BS may be referred to as an advanced base station (ABS),a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. Especially, a BS ofthe UMTS is referred to as a NB, a BS of the EPC/LTE is referred to asan eNB, and a BS of the new radio (NR) system is referred to as a gNB.

In the present disclosure, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of BSs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. maybe a node. In addition, the node may not be a BS. For example, the nodemay be a radio remote head (RRH) or a radio remote unit (RRU). The RRHor RRU generally has a lower power level than a power level of a BS.Since the RRH or RRU (hereinafter, RRH/RRU) is generally connected tothe BS through a dedicated line such as an optical cable, cooperativecommunication between RRH/RRU and the BS can be smoothly performed incomparison with cooperative communication between BSs connected by aradio line. At least one antenna is installed per node. The antenna mayinclude a physical antenna or an antenna port or a virtual antenna.

In the present disclosure, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present disclosure, communicating with a specificcell may include communicating with a BS or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to a BS or a node whichprovides a communication service to the specific cell. A node providingUL/DL communication services to a UE is called a serving node and a cellto which UL/DL communication services are provided by the serving nodeis especially called a serving cell.

In some scenarios, a 3GPP based system implements a cell to manage radioresources and a cell associated with the radio resources isdistinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage withinwhich a node can provide service using a carrier and a “cell” of a radioresource is associated with bandwidth (BW) which is a frequency rangeconfigured by the carrier. Since DL coverage, which is a range withinwhich the node is capable of transmitting a valid signal, and ULcoverage, which is a range within which the node is capable of receivingthe valid signal from the UE, depends upon a carrier carrying thesignal, the coverage of the node may be associated with coverage of the“cell” of a radio resource used by the node. Accordingly, the term“cell” may be used to indicate service coverage of the node sometimes, aradio resource at other times, or a range that a signal using a radioresource can reach with valid strength at other times.

In some scenarios, the recent 3GPP based wireless communication standardimplements a cell to manage radio resources. The “cell” associated withthe radio resources utilizes a combination of downlink resources anduplink resources, for example, a combination of DL component carrier(CC) and UL CC. The cell may be configured by downlink resources only,or may be configured by downlink resources and uplink resources. Ifcarrier aggregation is supported, linkage between a carrier frequency ofthe downlink resources (or DL CC) and a carrier frequency of the uplinkresources (or UL CC) may be indicated by system information. Forexample, combination of the DL resources and the UL resources may beindicated by linkage of system information block type 2 (SIB2). In thiscase, the carrier frequency may be a center frequency of each cell orCC. A cell operating on a primary frequency may be referred to as aprimary cell (Pcell) or PCC, and a cell operating on a secondaryfrequency may be referred to as a secondary cell (Scell) or SCC. Thecarrier corresponding to the Pcell on downlink will be referred to as adownlink primary CC (DL PCC), and the carrier corresponding to the Pcellon uplink will be referred to as an uplink primary CC (UL PCC). A Scellrefers to a cell that may be configured after completion of radioresource control (RRC) connection establishment and used to provideadditional radio resources. The Scell may form a set of serving cellsfor the UE together with the Pcell in accordance with capabilities ofthe UE. The carrier corresponding to the Scell on the downlink will bereferred to as downlink secondary CC (DL SCC), and the carriercorresponding to the Scell on the uplink will be referred to as uplinksecondary CC (UL SCC). Although the UE is in RRC-CONNECTED state, if itis not configured by carrier aggregation or does not support carrieraggregation, a single serving cell configured by the Pcell only exists.

In the present disclosure, “PDCCH” refers to a PDCCH, an EPDCCH (insubframes when configured), a MTC PDCCH (MPDCCH), for an RN with R-PDCCHconfigured and not suspended, to the R-PDCCH or, for NB-IoT to thenarrowband PDCCH (NPDCCH).

In the present disclosure, monitoring a channel refers to attempting todecode the channel. For example, monitoring a PDCCH refers to attemptingto decode PDCCH(s) (or PDCCH candidates).

For terms and technologies which are not specifically described amongthe terms of and technologies employed in this specification, 3GPPLTE/LTE-A standard documents, for example, 3GPP TS 36.211, 3GPP TS36.212, 3GPP TS 36.213, 3GPP TS 36.300, 3GPP TS 36.321, 3GPP TS 36.322,3GPP TS 36.323 and 3GPP TS 36.331, and 3GPP NR standard documents, forexample, 3GPP TS 38.211, 3GPP TS 38.213, 3GPP TS 38.214, 3GPP TS 38.300,3GPP TS 38.321, 3GPP TS 38.322, 3GPP TS 38.323 and 3GPP TS 38.331 may bereferenced.

FIG. 2 is a block diagram illustrating an example of an evolveduniversal terrestrial radio access network (E-UTRAN). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2 , the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipments (UE) 10may be located in one cell. One or more E-UTRAN mobility managemententity (MME)/system architecture evolution (SAE) gateways 30 may bepositioned at the end of the network and connected to an externalnetwork.

As used herein, “downlink” refers to communication from BS 20 to UE 10,and “uplink” refers to communication from the UE to a BS.

FIG. 3 is a block diagram depicting an example of an architecture of atypical E-UTRAN and a typical EPC.

As illustrated in FIG. 3 , an eNB 20 provides end points of a user planeand a control plane to the UE 10. MME/SAE gateway 30 provides an endpoint of a session and mobility management function for UE 10. The eNBand MME/SAE gateway may be connected via an S1 interface.

The eNB 20 is generally a fixed station that communicates with a UE 10,and may also be referred to as a base station (BS) or an access point.One eNB 20 may be deployed per cell. An interface for transmitting usertraffic or control traffic may be used between eNBs 20.

The MME provides various functions including NAS signaling to eNBs 20,NAS signaling security, access stratum (AS) Security control, Inter CNnode signaling for mobility between 3GPP access networks, Idle mode UEReachability (including control and execution of paging retransmission),Tracking Area list management (for UE in idle and active mode), PDN GWand Serving GW selection, MME selection for handovers with MME change,SGSN selection for handovers to 2G or 3G 3GPP access networks, roaming,authentication, bearer management functions including dedicated bearerestablishment, support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNB 20 and gateway 30 viathe S1 interface. The eNBs 20 may be connected to each other via an X2interface and neighboring eNBs may have a meshed network structure thathas the X2 interface.

As illustrated, eNB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 4 is a diagram showing an example of a control plane and a userplane of a radio interface protocol between a UE and an E-UTRAN based ona 3GPP radio access network standard. The control plane refers to a pathused for transmitting control messages used for managing a call betweenthe UE and the E-UTRAN. The user plane refers to a path used fortransmitting data generated in an application layer, e.g., voice data orInternet packet data.

Layer 1 (i.e. L1) of the 3GPP LTE/LTE-A system is corresponding to aphysical layer. A physical (PHY) layer of a first layer (Layer 1 or L1)provides an information transfer service to a higher layer using aphysical channel. The PHY layer is connected to a medium access control(MAC) layer located on the higher layer via a transport channel. Data istransported between the MAC layer and the PHY layer via the transportchannel. Data is transported between a physical layer of a transmittingside and a physical layer of a receiving side via physical channels. Thephysical channels use time and frequency as radio resources. In detail,the physical channel is modulated using an orthogonal frequency divisionmultiple access (OFDMA) scheme in downlink and is modulated using asingle carrier frequency division multiple access (SC-FDMA) scheme inuplink.

Layer 2 (i.e. L2) of the 3GPP LTE/LTE-A system is split into thefollowing sublayers: Medium Access Control (MAC), Radio Link Control(RLC) and Packet Data Convergence Protocol (PDCP). The MAC layer of asecond layer (Layer 2 or L2) provides a service to a radio link control(RLC) layer of a higher layer via a logical channel. The RLC layer ofthe second layer supports reliable data transmission. A function of theRLC layer may be implemented by a functional block of the MAC layer. Apacket data convergence protocol (PDCP) layer of the second layerperforms a header compression function to reduce unnecessary controlinformation for efficient transmission of an Internet protocol (IP)packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6)packet in a radio interface having a relatively small bandwidth.

The main services and functions of the MAC sublayer include: mappingbetween logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ; priority handling between logicalchannels of one UE; priority handling between UEs by dynamic scheduling;MBMS service identification; transport format selection; and padding.

The main services and functions of the RLC sublayer include: transfer ofupper layer protocol data units (PDUs); error correction through ARQ(only for acknowledged mode (AM) data transfer); concatenation,segmentation and reassembly of RLC service data units (SDUs) (only forunacknowledged mode (UM) and acknowledged mode (AM) data transfer);re-segmentation of RLC data PDUs (only for AM data transfer); reorderingof RLC data PDUs (only for UM and AM data transfer); duplicate detection(only for UM and AM data transfer); protocol error detection (only forAM data transfer); RLC SDU discard (only for UM and AM data transfer);and RLC re-establishment, except for a NB-IoT UE that only uses ControlPlane CIoT EPS optimizations.

The main services and functions of the PDCP sublayer for the user planeinclude: header compression and decompression (ROHC (Robust HeaderCompression) only); transfer of user data; in-sequence delivery of upperlayer PDUs at PDCP re-establishment procedure for RLC AM; for splitbearers in DC and LWA bearers (only support for RLC AM), PDCP PDUrouting for transmission and PDCP PDU reordering for reception;duplicate detection of lower layer SDUs at PDCP re-establishmentprocedure for RLC AM; retransmission of PDCP SDUs at handover and, forsplit bearers in DC and LWA bearers, of PDCP PDUs at PDCP data-recoveryprocedure, for RLC AM; ciphering and deciphering; timer-based SDUdiscard in uplink. The main services and functions of the PDCP for thecontrol plane include: ciphering and integrity protection; and transferof control plane data. For split and LWA bearers, PDCP supports routingand reordering. For DRBs mapped on RLC AM and for LWA bearers, the PDCPentity uses the reordering function when the PDCP entity is associatedwith two AM RLC entities, when the PDCP entity is configured for a LWAbearer; or when the PDCP entity is associated with one AM RLC entityafter it was, according to the most recent reconfiguration, associatedwith two AM RLC entities or configured for a LWA bearer withoutperforming PDCP re-establishment.

Layer 3 (i.e. L3) of the LTE/LTE-A system includes the followingsublayers: Radio Resource Control (RRC) and Non Access Stratum (NAS). Aradio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, reconfiguration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other. The non-access stratum (NAS) layer positioned over the RRClayer performs functions such as session management and mobilitymanagement.

Radio bearers are roughly classified into (user) data radio bearers(DRBs) and signaling radio bearers (SRBs). SRBs are defined as radiobearers (RBs) that are used only for the transmission of RRC and NASmessages.

In LTE, one cell of the eNB is set to operate in one of bandwidths suchas 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 5 is a diagram showing an example of a physical channel structureused in an E-UMTS system. A physical channel includes several subframeson a time axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. The PDCCH carries schedulingassignments and other control information. In FIG. 5 , an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one implementation, a radio frame of 10 ms is used and one radioframe includes 10 subframes. In addition, in LTE, one subframe includestwo consecutive slots. The length of one slot may be 0.5 ms. Inaddition, one subframe includes a plurality of OFDM symbols and aportion (e.g., a first symbol) of the plurality of OFDM symbols may beused for transmitting the L1/L2 control information.

A time interval in which one subframe is transmitted is defined as atransmission time interval (TTI). Time resources may be distinguished bya radio frame number (or radio frame index), a subframe number (orsubframe index), a slot number (or slot index), and the like. TTI refersto an interval during which data may be scheduled. For example, in the3GPP LTE/LTE-A system, an opportunity of transmission of an UL grant ora DL grant is present every 1 ms, and the UL/DL grant opportunity doesnot exists several times in less than 1 ms. Therefore, the TTI in thelegacy 3GPP LTE/LTE-A system is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a downlink shared channel (DL-SCH) which isa transmission channel, except a certain control signal or certainservice data. Information indicating to which UE (one or a plurality ofUEs) PDSCH data is transmitted and how the UE receive and decode PDSCHdata is transmitted in a state of being included in the PDCCH.

For example, in one implementation, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receives the PDSCH indicated by B and C in the PDCCHinformation. In the present disclosure, a PDCCH addressed to an RNTIrefers to the PDCCH being cyclic redundancy check masked (CRC-masked)with the RNTI. A UE may attempt to decode a PDCCH using the certain RNTIif the UE is monitoring a PDCCH addressed to the certain RNTI.

A fully mobile and connected society is expected in the near future,which will be characterized by a tremendous amount of growth inconnectivity, traffic volume and a much broader range of usagescenarios. Some typical trends include explosive growth of data traffic,great increase of connected devices and continuous emergence of newservices. Besides the market requirements, the mobile communicationsociety itself also requires a sustainable development of theeco-system, which produces the needs to further improve systemefficiencies, such as spectrum efficiency, energy efficiency,operational efficiency, and cost efficiency. To meet the aboveever-increasing requirements from market and mobile communicationsociety, next generation access technologies are expected to emerge inthe near future.

Building upon its success of IMT-2000 (3G) and IMT-Advanced (4G), 3GPPhas been devoting its effort to IMT-2020 (5G) development sinceSeptember 2015. 5G New Radio (NR) is expected to expand and supportdiverse use case scenarios and applications that will continue beyondthe current IMT-Advanced standard, for instance, enhanced MobileBroadband (eMBB), Ultra Reliable Low Latency Communication (URLLC) andmassive Machine Type Communication (mMTC). eMBB is targeting high datarate mobile broadband services, such as seamless data access bothindoors and outdoors, and AR/VR applications; URLLC is defined forapplications that have stringent latency and reliability requirements,such as vehicular communications that can enable autonomous driving andcontrol network in industrial plants; mMTC is the basis for connectivityin IoT, which allows for infrastructure management, environmentalmonitoring, and healthcare applications.

FIGS. 6A and 6B illustrate an example of protocol stacks of a nextgeneration wireless communication system. In particular, FIG. 6Aillustrates an example of a radio interface user plane protocol stackbetween a UE and a gNB and FIG. 6B illustrates an example of a radiointerface control plane protocol stack between a UE and a gNB.

The control plane refers to a path through which control messages usedto manage call by a UE and a network are transported. The user planerefers to a path through which data generated in an application layer,for example, voice data or Internet packet data are transported.

Referring to FIG. 6A, the user plane protocol stack may be divided intoa first layer (Layer 1) (i.e., a physical layer (PHY) layer) and asecond layer (Layer 2).

Referring to FIG. 6B, the control plane protocol stack may be dividedinto Layer 1 (i.e., a PHY layer), Layer 2, Layer 3 (e.g., a radioresource control (RRC) layer), and a non-access stratum (NAS) layer.

The overall protocol stack architecture for the NR system might besimilar to that of the LTE/LTE-A system, but some functionalities of theprotocol stacks of the LTE/LTE-A system should be modified in the NRsystem in order to resolve the weakness or drawback of LTE. RAN WG2 forNR is in charge of the radio interface architecture and protocols. Thenew functionalities of the control plane include the following:on-demand system information delivery to reduce energy consumption andmitigate interference, two-level (i.e. Radio Resource Control (RRC) andMedium Access Control (MAC)) mobility to implement seamless handover,beam based mobility management to accommodate high frequency, RRCinactive state to reduce state transition latency and improve UE batterylife. The new functionalities of the user plane aim at latency reductionby optimizing existing functionalities, such as concatenation andreordering relocation, and RLC out of order delivery. In addition, a newuser plane AS protocol layer named as Service Data Adaptation Protocol(SDAP) has been introduced to handle flow-based Quality of Service (QoS)framework in RAN, such as mapping between QoS flow and a data radiobearer, and QoS flow ID marking. Hereinafter the layer 2 according tothe current agreements for NR is briefly discussed.

The layer 2 of NR is split into the following sublayers: Medium AccessControl (MAC), Radio Link Control (RLC), Packet Data ConvergenceProtocol (PDCP) and Service Data Adaptation Protocol (SDAP). Thephysical layer offers to the MAC sublayer transport channels, the MACsublayer offers to the RLC sublayer logical channels, the RLC sublayeroffers to the PDCP sublayer RLC channels, the PDCP sublayer offers tothe SDAP sublayer radio bearers, and the SDAP sublayer offers to 5GC QoSflows. Radio bearers are categorized into two groups: data radio bearers(DRB) for user plane data and signalling radio bearers (SRB) for controlplane data.

The main services and functions of the MAC sublayer of NR include:mapping between logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ (one HARQ entity per carrier in case ofcarrier aggregation); priority handling between UEs by dynamicscheduling; priority handling between logical channels of one UE bylogical channel prioritization; and padding. A single MAC entity cansupport one or multiple numerologies and/or transmission timings, andmapping restrictions in logical channel prioritisation controls whichnumerology and/or transmission timing a logical channel can use.

The RLC sublayer of NR supports three transmission modes: TransparentMode (TM); Unacknowledged Mode (UM); Acknowledged Mode (AM). The RLCconfiguration is per logical channel with no dependency on numerologiesand/or TTI durations, and ARQ can operate on any of the numerologiesand/or TTI durations the logical channel is configured with. For SRB0,paging and broadcast system information, TM mode is used. For other SRBsAM mode used. For DRBs, either UM or AM mode are used. The main servicesand functions of the RLC sublayer depend on the transmission mode andinclude: transfer of upper layer PDUs; sequence numbering independent ofthe one in PDCP (UM and AM); error correction through ARQ (AM only);segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;Reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; and protocol error detection(AM only). The ARQ within the RLC sublayer of NR has the followingcharacteristics: ARQ retransmits RLC PDUs or RLC PDU segments based onRLC status reports; polling for RLC status report is used when needed byRLC; and RLC receiver can also trigger RLC status report after detectinga missing RLC PDU or RLC PDU segment.

The main services and functions of the PDCP sublayer of NR for the userplane include: sequence numbering; header compression and decompression(ROHC only); transfer of user data; reordering and duplicate detection;PDCP PDU routing (in case of split bearers); retransmission of PDCPSDUs; ciphering, deciphering and integrity protection; PDCP SDU discard;PDCP re-establishment and data recovery for RLC AM; and duplication ofPDCP PDUs. The main services and functions of the PDCP sublayer of NRfor the control plane include: sequence numbering; ciphering,deciphering and integrity protection; transfer of control plane data;reordering and duplicate detection; and duplication of PDCP PDUs.

The main services and functions of SDAP include: mapping between a QoSflow and a data radio bearer; marking QoS flow ID (QFI) in both DL andUL packets. A single protocol entity of SDAP is configured for eachindividual PDU session. Compared to LTE's QoS framework, which isbearer-based, the 5G system adopts the QoS flow-based framework. The QoSflow-based framework enables flexible mapping of QoS flow to DRB bydecoupling QoS flow and the radio bearer, allowing more flexible QoScharacteristic configuration.

The main services and functions of RRC sublayer of NR include: broadcastof system information related to access stratum (AS) and non-accessstratum (NAS); paging initiated by a 5GC or an NG-RAN; establishment,maintenance, and release of RRC connection between a UE and a NG-RAN(which further includes modification and release of carrier aggregationand further includes modification and release of the DC between anE-UTRAN and an NR or in the NR; a security function including keymanagement; establishment, configuration, maintenance, and release ofSRB(s) and DRB(s); handover and context transfer; UE cell selection andre-release and control of cell selection/re-selection; a mobilityfunction including mobility between RATs; a QoS management function, UEmeasurement report, and report control; detection of radio link failureand discovery from radio link failure; and NAS message transfer to a UEfrom a NAS and NAS message transfer to the NAS from the UE.

FIG. 7 illustrates a data flow example at a transmitting device in theNR system.

In FIG. 7 , an RB denotes a radio bearer. Referring to FIG. 7 , atransport block is generated by MAC by concatenating two RLC PDUs fromRB_(x) and one RLC PDU from RB_(y). In FIG. 7 , the two RLC PDUs fromRB_(x) each corresponds to one IP packet (n and n+1) while the RLC PDUfrom RB_(y) is a segment of an IP packet (m). In NR, a RLC SDU segmentcan be located in the beginning part of a MAC PDU and/or in the endingpart of the MAC PDU. The MAC PDU is transmitted/received using radioresources through a physical layer to/from an external device.

FIG. 8 illustrates an example of a slot structure available in a newradio access technology (NR).

To reduce or minimize data transmission latency, in a 5G new RAT, a slotstructure in which a control channel and a data channel aretime-division-multiplexed is considered.

In the example of FIG. 8 , the hatched area represents the transmissionregion of a DL control channel (e.g., PDCCH) carrying the DCI, and theblack area represents the transmission region of a UL control channel(e.g., PUCCH) carrying the UCI. Here, the DCI is control informationthat the gNB transmits to the UE. The DCI may include information oncell configuration that the UE should know, DL specific information suchas DL scheduling, and UL specific information such as UL grant. The UCIis control information that the UE transmits to the gNB. The UCI mayinclude a HARQ ACK/NACK report on the DL data, a CSI report on the DLchannel status, and a scheduling request (SR).

In the example of FIG. 8 , the region of symbols from symbol index 1 tosymbol index 12 may be used for transmission of a physical channel(e.g., a PDSCH) carrying downlink data, or may be used for transmissionof a physical channel (e.g., PUSCH) carrying uplink data. According tothe slot structure of FIG. 8 , DL transmission and UL transmission maybe sequentially performed in one slot, and thus transmission/receptionof DL data and reception/transmission of UL ACK/NACK for the DL data maybe performed in one slot. As a result, the time taken to retransmit datawhen a data transmission error occurs may be reduced, thereby minimizingthe latency of final data transmission.

In such a slot structure, a time gap is needed for the process ofswitching from the transmission mode to the reception mode or from thereception mode to the transmission mode of the gNB and UE. On behalf ofthe process of switching between the transmission mode and the receptionmode, some OFDM symbols at the time of switching from DL to UL in theslot structure are set as a guard period (GP).

In the legacy LTE/LTE-A system, a DL control channel istime-division-multiplexed with a data channel and a PDCCH, which is acontrol channel, is transmitted throughout an entire system band.However, in the new RAT, it is expected that a bandwidth of one systemreaches approximately a minimum of 100 MHz and it is difficult todistribute the control channel throughout the entire band fortransmission of the control channel. For data transmission/reception ofa UE, if the entire band is monitored to receive the DL control channel,this may cause increase in battery consumption of the UE anddeterioration in efficiency. Accordingly, in the present disclosure, theDL control channel may be locally transmitted or distributivelytransmitted in a partial frequency band in a system band, i.e., achannel band.

In the NR system, the basic transmission unit is a slot. A duration ofthe slot includes 14 symbols having a normal cyclic prefix (CP) or 12symbols having an extended CP. In addition, the slot is scaled in timeas a function of a used subcarrier spacing.

Hereinafter, RLC entities are explained.

RRC is generally in control of the RLC configuration. Functions of theRLC sub layer are performed by RLC entities. For an RLC entityconfigured at the gNB, there is a peer RLC entity configured at the UEand vice versa. An RLC entity receives/delivers RLC SDUs from/to upperlayer and sends/receives RLC PDUs to/from its peer RLC entity via lowerlayers.

An RLC PDU can either be an RLC data PDU or an RLC control PDU. If anRLC entity receives RLC SDUs from upper layer, it receives them througha single RLC channel between RLC and upper layer, and after forming RLCdata PDUs from the received RLC SDUs, the RLC entity submits the RLCdata PDUs to lower layer through a single logical channel. If an RLCentity receives RLC data PDUs from lower layer, it receives them througha single logical channel, and after forming RLC SDUs from the receivedRLC data PDUs, the RLC entity delivers the RLC SDUs to upper layerthrough a single RLC channel between RLC and upper layer. If an RLCentity submits/receives RLC control PDUs to/from lower layer, itsubmits/receives them through the same logical channel itsubmits/receives the RLC data PDUs through.

An RLC entity can be configured to perform data transfer in one of thefollowing three modes: Transparent Mode (TM), Unacknowledged Mode (UM)or Acknowledged Mode (AM). Consequently, an RLC entity is categorized asa TM RLC entity, an UM RLC entity or an AM RLC entity depending on themode of data transfer that the RLC entity is configured to provide.

A TM RLC entity is configured either as a transmitting TM RLC entity ora receiving TM RLC entity. The transmitting TM RLC entity receives RLCSDUs from upper layer and sends RLC PDUs to its peer receiving TM RLCentity via lower layers. The receiving TM RLC entity delivers RLC SDUsto upper layer and receives RLC PDUs from its peer transmitting TM RLCentity via lower layers. An UM RLC entity is configured either as atransmitting UM RLC entity or a receiving UM RLC entity. Thetransmitting UM RLC entity receives RLC SDUs from upper layer and sendsRLC PDUs to its peer receiving UM RLC entity via lower layers. Thereceiving UM RLC entity delivers RLC SDUs to upper layer and receivesRLC PDUs from its peer transmitting UM RLC entity via lower layers. AnAM RLC entity consists of a transmitting side and a receiving side. Thetransmitting side of an AM RLC entity receives RLC SDUs from upper layerand sends RLC PDUs to its peer AM RLC entity via lower layers. Thereceiving side of an AM RLC entity delivers RLC SDUs to upper layer andreceives RLC PDUs from its peer AM RLC entity via lower layers.

Especially, the TM RLC entity can be configured to submit/receive RLCPDUs through BCCH, DL/UL CCCH, and PCCH. The TM RLC entitysubmits/receives TMD PDU. When a transmitting TM RLC entity forms TMDPDUs from RLC SDUs, it shall not segment the RLC SDUs and not includeany RLC headers in the TMD PDUs. When a receiving TM RLC entity receivesTMD PDUs, it shall deliver the TMD PDUs (which are just RLC SDUs) toupper layer.

While, the UM RLC entity can be configured to submit/receive RLC PDUsthrough DL/UL DTCH. The UM RLC entity submits/receives the UMD PDU,which contains either one complete RLC SDU or one RLC SDU segment. Thetransmitting UM RLC entity generates UMD PDU(s) for each RLC SDU. Itshall include relevant RLC headers in the UMD PDU. When notified of atransmission opportunity by the lower layer, the transmitting UM RLCentity shall segment the RLC SDUs, if needed, so that the correspondingUMD PDUs, with RLC headers updated as needed, fit within the total sizeof RLC PDU(s) indicated by lower layer.

When a receiving UM RLC entity receives UMD PDUs, it shall detect theloss of RLC SDU segments at lower layers, reassemble RLC SDUs from thereceived UMD PDUs and deliver the RLC SDUs to upper layer as soon asthey are available, and discard received UMD PDUs that cannot bere-assembled into an RLC SDU due to loss at lower layers of an UMD PDUwhich belonged to the particular RLC SDU.

According to the prior art, all the PDCP PDUs generated in a PDCP entityis treated in a same manner regardless of the contents they include. Asthe same treatment is applied to all PDCP PDUs within a traffic flow, itis not possible to prioritize certain PDCP PDUs that include special orimportant information. For example, the SDAP control PDU may need to betransmitted faster and robustly than other SDAP data PDUs to reduce thereordering delay in the network side. The TCP (Transmission ControlProtocol) ACK packet may need to be transmitted faster and robustly thanother TCP packet to maintain or increase the throughput. PDCP ControlPDU may be another example that the prioritization within a traffic flowwould be beneficial.

Therefore, as a mechanism to prioritize certain PDCP PDUs, the presentapplication suggests that, for a transmitting PDCP entity, the UE shouldconfigure a special RLC entity, called “Prioritized RLC entity”, inaddition to the default RLC entity, and the transmitting PDCP entityshould submit special PDCP PDUs to the prioritized RLC entity whilesubmitting other PDCP PDUs to the default RLC entity.

The radio bearer (RB) is composed of a PDCP entity, a default RLCentity, and a prioritized RLC entity.

The mode of the prioritized RLC entity may be different from the mode ofthe default RLC entity. For example, the prioritized RLC entity isUnacknowledged Mode (UM) and the default RLC entity is Acknowledged Mode(AM). Even if the modes are same, the RLC parameters and state variablesmay be different.

Hereinafter, distinguished points between the prioritized RLC entity andthe default RLC entity are described.

Firstly, the logical channel priority of the prioritized RLC entity maybe different from that of the default RLC entity. For example, thelogical channel priority of the prioritized RLC entity is the highest(=1) and that of the default RLC entity is the lowest (=8). That is, apriority of the prioritized RLC entity is higher than a priority of thedefault RLC entity. The prioritized bit rate (PBR) of those logicalchannels may also be different.

Next, the prioritized RLC entity and the default RLC entity may belongto different Cell Groups (CG). For example, the prioritized RLC entitybelongs to Master Cell Group (MCG) and the default RLC entity belongs toSecondary Cell Group (SCG).

Next, the prioritized RLC entity and the default RLC entity may bemapped to different MAC entities. For example, the prioritized RLCentity is mapped to the MCG MAC entity and the default RLC entity ismapped to SCG MAC entity.

Next, the prioritized RLC entity and the default RLC entity may bemapped to different MAC entities. For example, the prioritized RLCentity is mapped to the MCG MAC entity and the default RLC entity ismapped to SCG MAC entity.

Further, the prioritized RLC entity and the default RLC entity may bemapped to different cells. For example, the prioritized RLC entity ismapped to a PCell and the default RLC entity is mapped to a SCell.

And, the prioritized RLC entity and the default RLC entity may be mappedto different logical channel groups (LCG). For example, the prioritizedRLC entity is mapped to LCG1 and the default RLC entity is mapped to LCG3.

Finally, the prioritized RLC entity and the default RLC entity may bemapped to different Scheduling Request (SR) resource configuration. Forexample, the prioritized RLC entity is mapped to SR configuration 1 andthe default RLC entity is mapped to SR configuration 2.

The special PDCP SDU is indicated from the upper layer when the PDCP SDUis received from the upper layer. The special PDCP SDU indication isprovided together with the PDCP SDU. If the special PDCP SDU indicationis received, the transmitting PDCP entity maps the PDCP SDU to a PDCPData PDU, and considers it to be a special PDCP PDU. The special PDCPPDU can be also configured by the network, defined in NR standard, ordecided by the PDCP entity.

Example of the special PDCP PDU is as follows:

-   -   PDCP PDU including SDAP Control PDU (e.g. end-marker)    -   PDCP PDU including TCP ACK    -   PDCP PDU including ROHC context update    -   PDCP Control PDU

Especially, the PDCP Control PDU is generated by the PDCP entity, andthus indication from the upper layer is not required.

When the transmitting PDCP entity receives a special PDCP SDU from anupper layer, or generates a PDCP Control PDU, the transmitting PDCPentity generates a special PDCP PDU including them, and submits it to aprioritized RLC entity associated with the transmitting PDCP entity. Forother types of PDCP SDUs, the transmitting PDCP entity generates normalPDCP PDUs, and submits them to a default RLC entity associated with thetransmitting PDCP entity.

When the transmitting PDCP entity receives a PDCP SDU from an upperlayer, the transmitting PDCP entity may apply different discard timervalues for special PDCP SDUs and normal PDCP SDUs. For example, 100 msdiscard timer value is applied for special PDCP SDUs and 10 ms discardtimer value is applied for normal PDCP SDUs. When the discard timerexpires, the transmitting PDCP entity discards the corresponding PDCPSDU, and provides discard indication to the prioritized RLC entity ifthe PDCP SDU is a special PDCP SDU, and provides discard indication tothe default RLC entity if the PDCP SDU is a normal PDCP SDU.

It is possible that multiple transmitting PDCP entities are mapped toone prioritized RLC entity. In this case, when a special PDCP PDU isreceived from a transmitting PDCP entity, the prioritized RLC entitygenerates an RLC PDU by including the PDCP entity ID or RB ID togetherwith the special PDCP PDU.

Further, it is also possible that a transmitting PDCP entity is mappedto one default RLC entity, and two or more prioritized RLC entities. Fora special PDCP PDU, the transmitting PDCP entity duplicates the specialPDCP PDU and submits them to multiple prioritized RLC entities. In otherwords, a normal PDCP PDU is not duplicated, but a special PDCP PDU isduplicated for transmission.

FIG. 9 shows an example about transmitting side operation using RLCentity prioritization according to an embodiment of the presentinvention.

Referring to FIG. 9 , it is shown that the UE configures an RB composedof one PDCP entity, one default RLC entity, and two prioritized RLCentities. The mode of the default RLC entity is AM, and the mode of theprioritized RLC entity is UM.

When the transmitting PDCP entity receives PDCP SDUs from the upperlayer, the transmitting PDCP entity checks whether the received PDCP SDUis a special PDCP SDU or a normal PDCP SDU. It is possible that thespecial PDCP SDU indication is received together with the PDCP SDU.

If the received PDCP SDU is a normal PDCP SDU, the transmitting PDCPentity generates a normal PDCP PDU including the normal PDCP SDU, andsubmits it to the default RLC entity. While, if the received PDCP SDU isa special PDCP SDU, the transmitting PDCP entity generates a specialPDCP PDU including the special PDCP SDU, duplicating it to two andsubmits them to the two prioritized RLC entity, respectively.

Each RLC entity transmits the RLC PDU to the receiving side. If theprioritized RLC entity is mapped to multiple transmitting PDCP entities,the prioritized RLC entity includes the PDCP entity ID or the RB ID inthe RLC PDU.

In the receiver side, the operation is in reverse order of thetransmitting side. The receiving PDCP entity receives normal PDCP PDUsfrom the default RLC entity, and receives special PDCP PDUs from theprioritized RLC entity.

The receiving PDCP entity does not perform reordering for the specialPDCP PDUs received from the prioritized RLC entity. In other words, whena PDCP PDU is received from a prioritized RLC entity and this PDCP PDUincludes a PDCP SDU, the receiving PDCP PDU delivers it to the upperlayer immediately after deciphering, integrity verification, or headerdecompression, if configured. On the other hand, the receiving PDCPentity performs reordering for the normal PDCP PDUs received from thedefault RLC entity.

If the PDCP PDU received from a prioritized RLC entity is a PDCP ControlPDU, the receiving PDCP entity does not perform reordering, but justparse the control information included in the PDCP Control PDU.

FIG. 10 shows a flow chart for transmitting signals by transmitting sideaccording to an embodiment of the present invention.

Referring to FIG. 10 , the transmission end configures one Packet DataConvergence Protocol (PDCP) entity, at least one first RLC entityrelated to the one PDCP entity and at least one second RLC entityrelated to the one PDCP entity, in S1001. Preferably, a priority of theat least one first RLC entity is higher than a priority of the at leastone second RLC entity.

Next, in S1003, the transmission end, especially, the PDCP entity of thetransmission end determines whether a Service Data Unit (SDU) to betransmitted is a special SDU or not. Here, the special SDU comprises atleast one of a Service Data Adaptation Protocol (SDAP) control SDU, aTransmission Control Protocol (TCP) ACK packet and a Robust HeaderCompression (ROHC) context update packet.

Next, if the SDU is not the special SDU, that is, if the SDU is thenormal SDU, the PDCP entity of the transmission end transmits the SDU toat least one second RLC entity in S1005.

While, if the SDU is the special SDU, the PDCP entity of thetransmission end transmits the special SDU to at least one first RLCentity in S1007. In this case, a PDCP entity of the reception enddelivers the special SDU to an upper layer without performing reorderingprocedure. More preferably, if the number of the at least one first RLCentity is greater than 1 and if the SDU is the special SDU, the specialSDU is duplicated as much as the number of the at least one first RLCentity, and the duplicated special SDUs are transmitted to the at leastone first RLC entity.

FIG. 11 is a block diagram illustrating an example of elements of atransmitting device 100 and a receiving device 200 according to someimplementations of the present disclosure.

The transmitting device 100 and the receiving device 200 respectivelyinclude transceivers 13 and 23 capable of transmitting and receivingradio signals carrying information, data, signals, and/or messages,memories 12 and 22 for storing information related to communication in awireless communication system, and processors 11 and 21 operationallyconnected to elements such as the transceivers 13 and 23 and thememories 12 and 22 to control the elements and configured to control thememories 12 and 22 and/or the transceivers 13 and 23 so that acorresponding device may perform at least one of the above-describedimplementations of the present disclosure.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers. The buffersat each protocol layer (e.g. PDCP, RLC, MAC) are parts of the memories12 and 22.

The processors 11 and 21 generally control the overall operation ofvarious modules in the transmitting device and the receiving device.Especially, the processors 11 and 21 may perform various controlfunctions to implement the present disclosure. For example, theoperations occurring at the protocol stacks (e.g. PDCP, RLC, MAC and PHYlayers) according to the present disclosure may be performed by theprocessors 11 and 21. The protocol stacks performing operations of thepresent disclosure may be parts of the processors 11 and 21.

The processors 11 and 21 may be referred to as controllers,microcontrollers, microprocessors, or microcomputers. The processors 11and 21 may be implemented by hardware, firmware, software, or acombination thereof. In a hardware configuration, application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs), orfield programmable gate arrays (FPGAs) may be included in the processors11 and 21. The present disclosure may be implemented using firmware orsoftware, and the firmware or software may be configured to includemodules, procedures, functions, etc. performing the functions oroperations of the present disclosure. Firmware or software configured toperform the present disclosure may be included in the processors 11 and21 or stored in the memories 12 and 22 so as to be driven by theprocessors 11 and 21.

The processor 11 of the transmitting device 100 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the transceiver 13. For example, the processor 11 converts a datastream to be transmitted into K layers through demultiplexing, channelcoding, scrambling, and modulation. The coded data stream is alsoreferred to as a codeword and is equivalent to a transport block whichis a data block provided by a MAC layer. One transport block (TB) iscoded into one codeword and each codeword is transmitted to thereceiving device in the form of one or more layers. For frequencyup-conversion, the transceiver 13 may include an oscillator. Thetransceiver 13 may include N_(t) (where N_(t) is a positive integer)transmission antennas.

A signal processing process of the receiving device 200 is the reverseof the signal processing process of the transmitting device 100. Undercontrol of the processor 21, the transceiver 23 of the receiving device200 receives radio signals transmitted by the transmitting device 100.The transceiver 23 may include N_(r) (where N_(r) is a positive integer)receive antennas and frequency down-converts each signal receivedthrough receive antennas into a baseband signal. The processor 21decodes and demodulates the radio signals received through the receptionantennas and restores data that the transmitting device 100 intended totransmit.

The transceivers 13 and 23 include one or more antennas. An antennaperforms a function for transmitting signals processed by thetransceivers 13 and 23 to the exterior or receiving radio signals fromthe exterior to transfer the radio signals to the transceivers 13 and23. The antenna may also be called an antenna port. Each antenna maycorrespond to one physical antenna or may be configured by a combinationof more than one physical antenna element. The signal transmitted fromeach antenna cannot be further deconstructed by the receiving device200. An RS transmitted through a corresponding antenna defines anantenna from the view point of the receiving device 200 and enables thereceiving device 200 to derive channel estimation for the antenna,irrespective of whether the channel represents a single radio channelfrom one physical antenna or a composite channel from a plurality ofphysical antenna elements including the antenna. That is, an antenna isdefined such that a channel carrying a symbol of the antenna can beobtained from a channel carrying another symbol of the same antenna. Antransceiver supporting a MIMO function of transmitting and receivingdata using a plurality of antennas may be connected to two or moreantennas. The transceivers 13 and 23 may be referred to as radiofrequency (RF) units.

In the implementations of the present disclosure, a UE operates as thetransmitting device 100 in UL and as the receiving device 200 in DL. Inthe implementations of the present disclosure, a BS operates as thereceiving device 200 in UL and as the transmitting device 100 in DL.Hereinafter, a processor, a transceiver, and a memory included in the UEwill be referred to as a UE processor, a UE transceiver, and a UEmemory, respectively, and a processor, a transceiver, and a memoryincluded in the BS will be referred to as a BS processor, a BStransceiver, and a BS memory, respectively.

The UE processor can be configured to operate according to the presentdisclosure, or control the UE transceiver to receive or transmit signalsaccording to the present disclosure. The BS processor can be configuredto operate according to the present disclosure, or control the BStransceiver to receive or transmit signals according to the presentdisclosure.

The processor 11 (at a UE and/or at a BS) checks whether there is a ULgrant or DL assignment for a serving cell in a time unit. If there is aUL grant or DL assignment for the serving cell in the time unit, theprocessor 11 checks whether a data unit is actually present on the ULgrant or DL assignment in the time unit, in order to determine whetherto restart a deactivation timer associated with the serving cell whichhas been started. The processor 11 restarts the deactivation timerassociated with the serving cell in the time unit if there is a dataunit present on the UL grant or DL assignment in the time unit. Theprocessor 11 does not restart the deactivation timer associated with theserving cell in the time unit if there is no data unit present on the ULgrant or DL assignment in the time unit, unless another condition thatthe processor 11 should restart the deactivation timer is satisfied. Theprocessor 11 does not restart the deactivation timer associated with theserving cell in the time unit if there is no data unit present on the ULgrant or DL assignment in the time unit and if an activation command foractivating the serving cell is not present in the time unit. Theprocessor 11 may be configured to check whether a data unit is actuallypresent on the UL grant or DL assignment on the serving cell in the timeunit in order to determine whether to restart the deactivation timer ofthe serving cell, if the UL grant or DL assignment is a configuredgrant/assignment which is configured by RRC to occur periodically on theserving cell. The processor 11 may be configured to check whether a dataunit is actually present on the UL grant or DL assignment on the servingcell in the time unit in order to determine whether to restart thedeactivation timer of the serving cell, if the UL grant or the DLassignment is a dynamic grant/assignment which is indicated by a PDCCH.The processor 11 may be configured to check whether a data unit isactually present on the UL grant or DL assignment on the serving cell inthe time unit in order to determine whether to restart the deactivationtimer of the serving cell, if the serving cell is a SCell of the UE. Theprocessor 11 (at the UE and/or the BS) deactivates the serving cell uponexpiry of the deactivation timer associated with the serving cell.

As described above, the detailed description of the preferredimplementations of the present disclosure has been given to enable thoseskilled in the art to implement and practice the disclosure. Althoughthe disclosure has been described with reference to exemplaryimplementations, those skilled in the art will appreciate that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure describedin the appended claims. Accordingly, the disclosure should not belimited to the specific implementations described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

The implementations of the present disclosure are applicable to anetwork node (e.g., BS), a UE, or other devices in a wirelesscommunication system.

What is claimed is:
 1. A method for processing signals by a Packet DataConvergence Protocol (PDCP) entity of a transmission end in a wirelesscommunication system, the method comprising: submitting a first dataunit not being related to negative acknowledgement (NACK) to one ofmultiple Radio Link Control (RLC) entities associated with the PDCPentity; receiving a second data unit to be transmitted from an upperlayer; and based on the second data unit being related to NACK,duplicating the second data unit and submitting the duplicated seconddata units to all of the multiple RLC entities associated with the PDCPentity.
 2. The method of claim 1, wherein, based on the second data unitbeing related to NACK, a PDCP entity of the reception end delivers thesecond data unit to an upper layer without performing reorderingprocedure.
 3. The method of claim 1, wherein duplicating the second dataunit comprises: duplicating the data unit as much as the multiple RLCentities.
 4. A user equipment (UE) configured to operate in a wirelesscommunication system, the UE comprising: at least one transceiver; atleast one processor; and at least one computer memory operablyconnectable to the at least one processor and storing instructions that,when executed, cause the at least one processor to perform operationscomprising: configuring a Packet Data Convergence Protocol (PDCP) entityand multiple Radio Link Control (RLC) entities associated with the PDCPentity; submitting a first data unit not being related to negativeacknowledgement (NACK) to one of the multiple RLC entities associatedwith the PDCP entity; receiving a second data unit to be transmittedfrom an upper layer; and based on the second data unit being related tonegative acknowledgement (NACK), duplicating the second data unit andsubmitting the duplicated second data units to all of the multiple RLCentities associated with the PDCP entity.
 5. The UE of claim 4, wherein,based on the second data unit being related to NACK, a PDCP entity ofthe reception end delivers the second data unit to an upper layerwithout performing reordering procedure.
 6. The UE of claim 4, whereinduplicating the second data unit comprises: duplicating the second dataunit as much as the multiple RLC entities.